The invention relates to a device for releasably connecting and adjusting the camshaft and the crankshaft of an internal combustion engine, having an adjusting gear created as a three shaft transmission, which has a drive shaft connected with the crankshaft, an output shaft connected with the camshaft, and an adjusting shaft connected with an electric adjusting motor, in which there is a gear transmission ratio io between the drive shaft and the output shaft when the adjusting shaft is at rest, and the magnitude of the gear transmission ratio is determined by the gear type and the direction of setting of the camshaft, which has a base or emergency running position.
To ensure a secure starting in motion of an internal combustion engine with a hydraulic and electrical adjusting system for the camshaft, the camshaft must find itself in a so-called base or emergency running position. This position usually lies with the inlet camshafts in a “late”, and the outlet camshafts in “early” positions. In normally functioning vehicles, the camshaft is set to the base position by turning off the motor and then fixing and locking it.
A conventional, hydraulically activated rotating piston adjuster, in the form of pivoting vanes or segment wings has a locking device. This unit fixes the hydraulic adjuster in its base position until it collects enough oil pressure to be able to set the camshaft. If an engine stall occurs, the camshaft can be in an undefined position outside the base position.
For hydraulic camshaft adjusting systems with a base position that is “late”, during the next starting of the internal combustion engine, when the oil pressure is not sufficient because of the friction moment of the camshaft, which works in the opposite direction, the camshaft is set automatically to the late base position. If the base position is “early”, when the oil pressure is not sufficient, the camshaft must be adjusted against the friction moment of camshaft to the early base position. This happens mostly through the use of a compensating spring, which creates the same but opposite moment to the camshaft friction moment.
These methods, common for hydraulically driven camshaft adjusters to achieve the base position after stalling an internal combustion engine, cannot be applied for electrically driven camshaft adjusters. They are also not necessary as long as the system of adjusting the motor is intact and can adjust the camshaft to the base position when an internal combustion engine is at rest or is started again. But in case of electric adjusting systems, the adjusting motor and/or its controlling system can fail and therewith impede the reaching of the base position.
There is a device described in DE 41 10 195 A1 for releasably connecting and adjusting the camshaft and the crankshaft of an internal combustion engine with an adjusting gear created as a three shaft transmission, which has a drive shaft connected with the crankshaft, a drive shaft connected with the camshaft, and an adjusting shaft connected with an electric adjusting motor, whereas there is a gear transmission ratio io between the drive shaft and the output shaft when the adjusting shaft is at rest, and magnitude of the gear transmission ratio is determined by the type of gear (minus or plus gear) and the adjusting direction of camshafts, that have a base or emergency running position.
In this adjusting device the goal is an easy working and precise adjusting of the camshaft position. In order to maintain at least a basic functioning of the internal combustion engine, when the adjusting motor's system fails, it is designed as a limitation of the setting angle. Nevertheless, there is no indication in such a case when the base or emergency running position is reached.